Carbon nanotubes possess numerous desirable properties including excellent mechanical strength, sensitivity to their surroundings, ability to carry high currents, and distinct absorption and luminescence peaks. These properties have been exploited in a wide range of applications such as transistors and interconnects in electrical circuits, mechanical oscillators, sensors, and solar cells. In an effort to enhance their properties and thus enable further applications, a variety of schemes have been developed for covalently and noncovalently functionalizing carbon nanotubes. In many cases, noncovalent functionalization is preferred since it retains the superlative properties of the underlying nanotube.
A variety of metals (e.g., gold (Au), platinum (Pt), palladium (Pd), and copper (Cu)) have been successfully affixed to carbon nanotubes. In particular, Pt nanoparticles have been bound to nanotubes via Pt evaporation or electrodeposition on nanotube mats, binding to functional groups on the nanotube surface or an encapsulating polymer, and physisorption. Deposition of Pt on carbon nanotubes has been shown to increase chemical reactivity (e.g., catalytic activity and hydrogen storage capacity) compared to carbon black substrates and holds promise for improved hydrogen storage devices and fuel cells. For these applications, Pt nanoparticle growth on dispersed carbon nanotubes is desirable because it enables enhanced surface coverage, reactant accessibility, and surface area-to-volume ratio.
However, the above prior art methods present various drawbacks such as weak bonding, limited surface area-to-volume ratio, and nanotube surface damage that can degrade the desirable optoelectronic performance of unperturbed (or pristine) nanotubes. Accordingly, there is a need in the art for new methods to functionalize carbon nanotubes with metallic moieties that can overcome at least some of these drawbacks.